Marked up README.

Now using reStructuredText. Cleaned up a few text errors.  Added link to
travis test status.

README → README.rst

-Crontab linter.
+==========
+chkcrontab
+==========
+.. image:: https://secure.travis-ci.org/lyda/chkcrontab.png
+   :target: https://secure.travis-ci.org/lyda/chkcrontab
+   :alt: Build status
+
+Crontab linter
+==============
 
 chkcrontab is a script to check crontab files like those in
-/etc/cron.d and /etc/crontab.  It tries to catch glaring errors
-and warn on suspect lines in a crontab file.  Some valid lines
-will generate warnings.  Certain silly yet valid crontab lines
+``/etc/cron.d`` and ``/etc/crontab``.  It tries to catch glaring
+errors and warn on suspect lines in a crontab file.  Some valid
+lines will generate warnings.  Certain silly yet valid crontab lines
 will generate errors as well.
 
-Run this by doing ./chkcrontab crontab_file
+Run this by doing::
+
+    chkcrontab crontab_file
 
 Errors will cause a non-zero exit code.  Warnings alone will not.
 
-To see sample output for a bad crontab, run the following:
+To see sample output for a bad crontab, run the following::
 
   ./chkcrontab ./tests/test_crontab
 
-See the ./tests/test_crontab.disable crontab for how to disable
+See the ``./tests/test_crontab.disable`` crontab for how to disable
 warnings and errors.
 
-CONTRIBUTIONS
+Contributions
+=============
 
 Please add unit tests for new features or bug fixes.  To run all
-the unitests run ./setup test.
+the unit tests run ``./setup test``.